Ubiquitous use of the World Wide Web (WWW) and a wide range of Internet services has caused Internet traffic to grow exponentially. Traffic from real-time/mission-critical applications co-exists with non-real-time applications over an Internet infrastructure that provides best-effort service to both kinds of traffic. When Internet traffic is high, performance of bandwidth/delay-sensitive applications can deteriorate.
Quality of Service (QoS) refers to performance experienced by end-users and applications. QoS is measured in various ways and generally is dependent on the service requirements of end-users and applications. Such requirements may pertain, for example, to time taken to service a query with a response, ability to effectively perform distributed cooperative control, acceptable audio quality for voice calls using IP telephony, and satisfactory video quality for real-time video presentations.
There also has been tremendous growth in mobile ad hoc wireless networks, including but not limited to satellite communication networks in commercial and military communication environments. These wireless mobile communication networks are subject to rapidly changing network topology and link bandwidth that can affect QoS performance for end-users and applications.